Abu Dawud Book 34, Hadith Number 4490.

Chapter : If the legal heir of a man who has been killed intentionally agrees to accept bloodwit the slayer will be asked to pay him.

Narated By Abu Hurairah : When Mecca was conquered, the Apostle of Allah (may peace be upon him) got up and said: If a relative of anyone is killed, he will have the choice between the two: he (the slayer) will either pay the blood-wit or he will be killed. A man of the Yemen called Abu Shah stood up and said: Write for me, Apostle of Allah. The narrator al-‘Abbas (b. al-Walid) said: Write for me, (you people). The Apostle of Allah (may peace be upon him) said: Write (you people) for Abu Shah These are the wordings of the tradition of Ahmad.

Abu Dawud said: Write (you people), (or me, that is, the address of the Prophet (may peace be upon him).